A flat-panel CRT display basically consists of an electron-emitting device and a light-emitting device that operate at low internal pressure, typically from 10−6 torr to 10−2 torr. The electron-emitting device, commonly referred to as a cathode, contains electron-emissive elements allocated into a group of laterally separated electron-emissive regions for emitting electrons over a relatively wide area. The emitted electrons are directed towards light-emissive regions distributed over a corresponding area in the light-emitting device. Upon being struck by the electrons, the light-emissive regions emit light that produces an image on the viewing surface of the display.
The electron-emissive elements need to be clean during display operation. Contaminants that build up on the surfaces of the electron-emissive elements act to increase the height and/or width of the electron tunneling barriers. This leads to higher operating voltages for the displays, and attendant emission degradation. Also, contamination of the electron-emissive surfaces produces emission non-uniformity and leads to undesirable image artifacts. Degraded display performance, even display failure, is commonly the result.
Various techniques have been reported for cleaning electron-emissive elements in flat-panel CRT displays. For example, see U.S. Pat. Nos. 5,635,790 and 6,004,180. The cleaning techniques described in these two patents are performed during display fabrication and thus prior to final display sealing including evacuation to the desired initial internal display pressure. The cleaning techniques may, as occurs in some of the techniques described in U.S. Pat. No. 6,004,180, entail operating the electron-emissive elements. Nonetheless, the cleaning techniques are still completed prior to final display sealing.
In addition to becoming contaminated during display fabrication, electron-emissive elements in a flat-panel CRT display also become contaminated during display operation subsequent to final display sealing. For instance, material that contaminates the electron-emissive elements can be released from the display's light-emitting device when it is struck by electrons emitted by the display's electron-emitting device. Accordingly, it would be desirable to have technique for cleaning a flat-panel CRT display during display operation subsequent to final display sealing.